1. Field of the Invention
The present invention relates to a rotary connection device assembled in, for example, a steering device of an automobile, to be used as a means for electrically connecting a steering wheel side (rotary side) and a body side (fixed side).
2. Description of the Related Art
An example of an automobile will be explained. As shown in FIG. 6, a rotary connection device comprises a rotary side member 1 to be rotated integrally with a steering shaft, a fixed side member 2 fixed on the body side (hereinafter, according to common names, the rotary side member 1 is referred to as a rotor, and the fixed side member 2 as a case), a flat cable 4 provided in a cable storage space 3 formed therebetween, and a terminal (not illustrated) for drawing out the flat cable 4 to the outside, so as to be used for connection of electric parts of a horn switch, an air bag, or the like.
In FIG. 6, the numeral 5 denotes a cylindrical rotor boss provided in the center part of the rotor 1, projecting to the case 2 side such that the steering shaft is inserted through the rotor boss 5. Moreover, the flat cable 4 is provided in the state spirally wound around the rotor boss 5. The numeral 6 denotes a stopping ring for interlocking the rotor 1 and the case 2 in the axial direction.
However, in the rotary connection device, a problem is involved in that the cable 4 swayed in the axial direction due to vibration of the car body, or the like, is collided against the rotor 1 or the case 2 so as to generate a noise.
Conventionally, as a countermeasure therefor, a technique for restraining the backlash of the cable in the axial direction by providing a plastic sleeve formed in a cylindrical shape with a collar in the state with the collar part elastically pressuring the flat cable in the axial direction as disclosed in JP-B-62-124785 has been proposed.
However, according to the prior art, since the elastic deformation of the entirety of the collar part according to the contact pressure with the cable is utilized, it is extremely difficult to both satisfy the request for a large elastic deformation stroke including a margin for absorbing a part error and an assembly error, and the request for ensuring a necessary and sufficient pressuring force. Therefore, problems are generated in that the backlash prevention effect for the cable is lowered due to an insufficient pressuring force, or in contrast, that a free movement of the cable is inhibited or the elastic deformation stroke is insufficient due to an excessive pressuring force.
As another technique to take its place, it is conceivable to provide a flexible elastic member such as a foamed urethane, capable of taking a large elastic deformation stroke, molded in a thick sheet-like shape, on the inner surface of a rotor. However, even in this case, as long as the elastic deformation motion of the entirety of the elastic member is utilized, it is also extremely difficult to both satisfy a necessary deformation stroke and an appropriate pressuring force, partially due to the limit on the elastic member thickness.
Accordingly, an object of the invention is to provide a rotary connection device capable of ensuring both necessary elastic deformation stroke and appropriate pressuring force in an elastic member in a configuration wherein a cable is pressured elastically in the axial direction by the elastic member.
A first aspect of the invention is a rotary connection device comprising first and second members fitted in the state both relatively rotatable around the same axis with a cable storage space formed therebetween such that a cable for electric conduction stored in the cable storage space in the wound state, wherein an elastic member for elastically pressuring the cable in the axial direction against the cable facing surface of at least one of the first and second members, facing the cable in the axial direction is provided in the state partially elastically deformable in the axial direction with respect to the entirety of the cable facing surface by the contact pressure with the cable.
A second aspect of the invention is the rotary connection device according to the first aspect, wherein the first member is a fixed side member mounted on a fixed part, the second member is a rotary side member mounted on a rotary part, and the cable is a flat cable, with the flat cable spirally wound in the cable storage space.
A third aspect of the invention is the rotary connection device according to the first or second aspect, wherein projections are provided in plural parts of the cable facing surface of the member provided with the cable, and a sheet-like elastic member is provided across the projections in the state elastically deformable at the part contacting with the projections.
A fourth aspect of the invention is the rotary connection device according to the third aspect, wherein a plurality of ribs are arranged as the projections radially with respect to the rotation center of the member provided with the cable.
A fifth aspect of the invention is the rotary connection device according to the third or fourth aspect, wherein the elastic member is provided on the cable on the side of either of the first and second members provided above, independently therefrom.
A sixth aspect of the invention is the rotary connection device according to the first or second aspect, wherein the elastic member is provided at plural points on the cable facing surface.
A seventh aspect of the invention is the rotary connection device according to any of the first to sixth aspects, wherein a sliding layer for smoothly sliding the cable is provided on the surface of the elastic member contacting with the cable.
An eighth aspect of the invention is the rotary connection device according to the seventh aspect, wherein the sliding layer is provided on the substantial entirety of the cable facing surface.
According to the configuration, since the elastic member for pressuring the cable in the axial direction for restraining the backlash is elastically deformed partially with respect to the cable facing surface according to the contact pressure with the cable (only the part in the elastic member provided across the plurality of the projections contacting with the projections is deformed elastically in the third and fourth aspects, and the plurality of the elastic members provided dispersively are elastically deformed independently in the sixth aspect), compared with the case of elastic deformation of the elastic member in the entire area of the cable facing surface, the elastic deformation stroke can be large. Besides, the pressuring force of the elastic member can be adjusted freely according to the area wherein the contact pressure is applied, or the like.
That is, antinomic demand for a large elastic deformation stroke including the margin for absorbing the errors, and an appropriate pressuring force not restraining the free movement of the cable can easily be satisfied at the same time.
Accordingly, while maintaining the rotary connection function inherent to the rotary connection device, generation of noises due to sway of the cable in the axial direction can be restrained. In particular, a high effect can be provided in a rotary connection device to be assembled in a steering device of an automobile with much vibration.
Moreover, according to the configuration of the third, fourth, and fifth aspects, since the elastic member is provided across the plurality of the projections (ribs in the fourth aspect), compared with the case of partially providing the same (the sixth aspect), the assembly operation can be facilitated. In particular, the effect thereof is significant in the fifth aspect wherein the elastic member only needs to be placed on the cable.
In contrast, according to the configuration of the sixth aspect, since the elastic members are elastically deformed independently, the deformation stroke and the pressuring force can be adjusted easily as well as the adjustment width to the optimal value can be wide.
In contrast, according to the configuration of the seventh and eighth aspects, since a sliding layer is provided on the contact surface of the elastic member with respect to the cable, even in the case the pressuring force is slightly strong, or the like, the cable movement cannot be inhibited. In particular, since the sliding layer is provided on the substantial entirety of the cable facing surface in the eighth aspect without a part lacking the sliding effect of the sliding layer, the free movement of the cable can certainly be ensured.